There are numerous instances where a series of sheet or panel-type products need be transported and/or stored. When all such items are identical, there is usually no need to be concerned over loading and unloading sequences. However, when the items are not identical, any sequenced access must be predetermined which usually entails predetermined loading strategies and, furthermore, random access may simply not be possible. Moreover, where the items vary in thickness, group clamping typically requires individual (i.e. time-consuming) adjustment of respective clamping mechanisms. Existing solutions are either cumbersome, inefficient and/or unable to address all of the user-defined requirements. These requirements and the challenges were, mainly, the following:                the ability to load a variety of panel sizes and thicknesses within a given packaging unit, for example in a custom metal rack;        the ability to access, remove or replace any one or all panels individually, without affecting the rest of the panels;        the ability to grip and hold the parts (panels) during transport and storage;        user-friendly operating sequences;        reliability and ease of maintenance; and        cost effectiveness.        
U.S. Pat. No. 2,946,453 describes a supporting rack for automobile windshields having a plurality of pairs of posts, half of which are fixed while the other half are associated with a movable frame so as to enable the movable posts to be moved in unison against the fixed posts to provide a clamping action therebetween.
U.S. Pat. No. 2,953,253 illustrates a windshield carrier having a pair of fixed parallel slotted frames for receiving windshields therein. Clamping is effected either by an associated pair of movable parallel frames having corresponding slots therein (FIG. 1) or a series of pressure elements movable through a linkage (FIG. 8). The devices of both of these patents have unitary movement of all clamping elements, but the fixed spacing structure will only function to clamp the thickest of a plurality of planar articles of variable thicknesses.
U.S. Pat. No. 4,093,251 discloses a windshield carrier having a plurality of posts in two rows. A rotatable friction element is disposed atop each post which can be rotated into engagement with the surface of a windshield disposed between adjacent posts. The friction elements are individually rotatable. This device has the capacity to accommodate a plurality of planar articles of variable thicknesses, but each clamping mechanism must be operated independently.
U.S. Pat. No. 4,202,452 shows a supporting rack for breakable articles comprising a plurality of spaced apart posts in parallel rows. An inflatable tube is provided on the exterior of each post and, thus, between adjacent posts. The tube is inflatable to contact the articles disposed between the posts in a secure and safe fashion. This apparatus has the capacity to accommodate a plurality of planar articles of variable thicknesses and is operable to close and release all clamps in unison. However, the apparatus requires the hydraulic/pneumatic system to be operating/pressurized at all times when clamping is required. Thus, if the system fails, the clamping function ceases.
U.S. Pat. No. 4,785,936 illustrates a device for holding flat objects, such as circuit boards, wherein a plurality of slots are provided in a tray having cooperating blocks with ridges moveable relative thereto. In order to accommodate a variety of thicknesses of boards, resilient cushions are disposed between the ridges which compress to the extent necessary. The device is spring biased in the open position. This device has the capacity to accommodate a plurality of planar articles of variable thicknesses and is operable to close and release all clamps in unison. Like with U.S. Pat. No. 4,202,452, this apparatus is open in its relaxed state.